1. Field of the Invention
The present invention relates to a printing medium that can also store electronic data, to an image forming apparatus for printing an image on the printing medium, and to a method of printing on the printing medium, more particularly to a method that deters counterfeiting.
2. Description of the Related Art
The increasing quality of the images turned out by color copiers and other image forming apparatus has made the creation of faithful copies of printed matter a simple undertaking. There is accordingly a need for printing media equipped with effective means of preventing counterfeiting, that is, of preventing the illegal copying and use of printed matter having negotiable value, such as tickets and securities. Known means include both means for validating the image or information printed on the printing medium, and means that make the printing medium intrinsically difficult to copy. Both means may be employed simultaneously.
Known validation methods include the printing of a bar code generated from the printing data from which the printed image is generated, and the addition of predetermined information to the printing data, so that the printed image provides its own validation information. Known methods of making the printing medium difficult to copy include the addition of an optically variable mark such as a hologram to the printing medium. In a further method, disclosed in Japanese Unexamined Patent Application Publication No. 2000-285203, an integrated circuit (IC) chip is embedded in the printing medium to store validation data electronically; the validation data can be read from the IC chip to verify that the document printed on the printing medium is genuine.
Printing media incorporating an IC chip are secure from counterfeiting by image forming apparatus, because an image forming apparatus cannot copy the data stored in the IC chip, but such printing media are not useful unless they provide means of read and write access to the IC chip. In the above disclosure, read access and write access are virtually unrestricted, making it impossible to protect the secrecy of the data recorded in the IC chip. A suitably equipped counterfeiter can make an accurate copy of the negotiable security, ticket, or other image printed on the printing medium, then read the data recorded in the embedded IC chip and write identical data into a similar IC chip embedded in the copy, thereby producing a counterfeit copy that is substantially indistinguishable from the genuine original.